fix(iac): drop vms/ — Orca does not provision VMs

Re-read the Orca spec: 'orca nodes' lists already-joined hosts and
'orca join' attaches an existing node to a cluster, but Orca does not
provision the VMs themselves. VM provisioning (SysEleven OpenStack
via Terraform) is a separate concern and will land in a dedicated repo
under the M1.2 milestone, not in orca-platform.

Removes vms/{vm-edge,vm-control,vm-data,stage}.toml + vms/README.md.
Updates README directory tree and milestone fill-in table to reflect
that M1.2's VM specs live elsewhere. validate.sh stops checking vms/.

Refs: M1.1

scripts/validate.sh

@@ -49,13 +49,6 @@ for p in sorted(root.glob('overlays/*/overlay.toml')):
         tomllib.load(open(p, 'rb'))
     except Exception as e:
         errs.append(f'{p}: TOML parse: {e}')
-# Validate VMs parse too
-for p in sorted(root.glob('vms/*.toml')):
-    count += 1
-    try:
-        tomllib.load(open(p, 'rb'))
-    except Exception as e:
-        errs.append(f'{p}: TOML parse: {e}')
 print(f'checked {count} files')
 for e in errs:
     print('  ', e)